Motor brush assembly



Feb. 4, 1936. s. N. MEAD 2,029,782

v MOTOR BRUSH ASSEMBLY Filed May 25, 1954 il ggf MN5/mmm nifl/l;

I n lNvr-:Nro SAMUEL NELSON MEAD BY 7,' 3 ATTORNEY Patented Feb. 4, 1936UNITED STATES PATENT OFFICE Application May 25,

Claims.

This invention relates to a motor brush assembly and has for its objectto provide an assembly suitable for use in connection with moistureproof or dust proof motors.

Another object is to provide a brush which will maintain contact with aslip ring regardless of any shock which the motor brush may be subjectedto.

Still another object is to provide an inexpensive assembly of brushes ina single unit which can be removed from the motor with a minimum ofetort, and which when in place acts as a closure that serves to seal themotor making it dust and moisture proof.

The present invention is suitable for use in connection with smallsynchronous motors used to operate indicating and control devices.

The armatures of such motors must be capable of rotating with a veryslight amount of friction in order to operate accurately. On board ship,

especially battle ships, where accurate operation is essential, it hasbeen found that vibration of engines and shock of gunfire have atendency to jar the brushes of such motors out of contact with the sliprings thus causing erratic and unreliable operation of the indicatingsystem.

If pressure of the brushes on the slip rings be increased suiiciently toovercome this diii'iculty, the added friction will greatly reduce theeniciency of the motor. Accordingly a further object of this inventionis to provide a brush which will maintain contact with very slightpressure on the slip rings.

Referring to the drawing:

Figure 1 is a section taken through I-I of Fig. 2.

Figure 2 is a top view of the assembly.

Both figures are shown considerably enlarged for the sake of clearness.

The invention consists of a cover or plate 2 which serves as a base forthe brush assembly. This base is adapted to t over a suitably situatedopening in the motor case (not shown) to which it may be secured by anyconvenient means such as by screws. Reference characters 3 indicateholes for such screws. If desired a gasket may be placed between theplate 2 and the motor casing.

The drawing sho-ws a brush assembly suitable for use in connection witha three phase indicating motor. 'I'hree sets of brushes are provided.

Plate 2 is made, preferably, of somel molded insulating material such asbakelite. In the present embodiment, the plate is formed so as to havenear its central portion four raised sections or 193.4, Serial No.727,387

fins on each side, 4, 5, 6 and I on the inner side of the plate formingthree channels in which the respective brushes are mounted; the raisedsections serving to insulate the brushes from each other. On the outerside of the plate, the lugs connected to the respective brushes areinsulated by corresponding raised sections 8, 9, I0, and II.

Each brush consists of two blades, I2 and I3, both being substantiallyL-shaped with their shorter ends, I4 and I5 freely movable on a commonpivot I6, in a slot 20 in a piece of brass, or other suitable metal 2|.The latter is of the same general shape as the i'lns 4, 5, Ii, and 1,but smaller in size, and of such thickness that it fits snugly betweenany of the adjacent pairs of ns. Each member 2| is secured in itsparticular slot by a screw 23. Obviously, with the construction justdescribed one screw is suflicient to hold each brush in place becausethe ns separating the brushes prevent them from turning and at the sametime serve to insulate the brushes from each other.

The brushes are connected to external circuits by means of screws 24which pass through holes in base 2 and are threaded into members 2|.Lugs 25 are secured by screws 24, and are insulated from each other bythe fins 9, III, and II.

Sections 26 of each pair of brushes I2 and I3 are rounded off at the endin order to make it easier to slip the brushes over the slip rings 21when the assembly is being set in position. Sections 26 make contactwith a slip ring at substantially diametrically opposite points, wherethey are held in contact by spring 28 which connects the two brushblades. 'I'he larger dotted ring 29 in Fig. 1 represents a raisedinsulating ring between the motor slip rings.

'I'he brush just described operates as follows:

Spring 28 has just sufficient tension to hold both brushes I2 and I3 incontact with slip ring 21. Due to the fact that only the relatively thinedges of the blades ride on the ring, friction is reduced to a minimum.If the motor be subjected to a shock of such a nature as to tend to jarone brush out of contact, the other brush will be more firmly heldagainst the slip ring due to an increased tension on the brush spring.

Due to the novel construction disclosed the D parts of the brushes inengagement with the slip rings have a certain amount of side play whichtends to prevent the relatively narrow edges of the brushes from wearinggrooves in the slip ring. Pig tail connections may be provided betweenthe brush blades and the slotted member 2| according to well knownpractice.

I claim:

1. A motor brush assembly comprising in combination a base, a pluralityof independent brushes, each brush consisting of a pair of flat metalblades extending from said base to engage edgewise the opposite sides ofa slip ring of a motor, and a retractile spring connecting therespective blades of each brush.

2. A motor brush assembly comprising a base, a plurality of independentbrushes, each brush consisting of a pair of blades of flat metal, meansfor pivoting one end of each blade at the base so that the blades extendtherefrom to engage edgewise the opposite sides of a. slip ring of a.motor, and a retractile spring connecting the respective blades of eachbrush to hold them in contact with said slip ring.

3. A motor brush assembly comprising a base, a plurality of independentbrushes, each brush consisting of a pair of blades of flat metal, a

plurality of channels formed in said base for separating the respectivebrushes, means for pivotally mounting one end of each blade at the baseso that the blades extend therefrom to engage edgewise opposite sides ofa slip ring of a motor, and a spring located between said mounting andslip ring tending to draw the blades together.

4. A motor brush assembly comprising a base, a plurality of independentbrushes, each brush consisting of a pair of blades of ilat metal, asingle pivot for mounting each pair of blades at the base so that theblades extend from the base to engage edgeWise opposite ends of adiameter of a slip ring of a motor, and a retractile spring connectingboth blades of a brush located between said pivot and the slip ring.

5. A motor brush comprising a pair of flat blades, a common pivot forsupporting said blades so that they engage edgewise opposite sides of a20 slip ring.

`SAMUEL NELSON MEAD.

